Frequency hopping is commonly used in high-frequency wireless communication systems to reduce interference. In some frequency bands, frequency hopping is employed in order to meet regulatory requirements, such as Federal Communications Commission (FCC) Part 15B. The Bluetooth® wireless system, which operates in the unlicensed ISM band at 2.4 GHz, uses frequency hop transceivers to combat interference and fading. Bluetooth is described in the Specification of the Bluetooth System, vol. 1, version 1.2 (Bluetooth SIG, Inc., 2003), which is available at www.bluetooth.com.
Bluetooth technology provides the effect of full duplex transmission through the use of a time-division duplex (TDD) scheme. In this scheme, the physical channel is sub-divided into time units known as slots. Data are transmitted between Bluetooth devices in packets, which are positioned in these slots. When circumstances permit, a number of consecutive slots may be allocated to a single packet. Frequency hopping takes place between the transmission or reception of packets. Bluetooth provides a number of different logical transport protocols, among them the extended synchronous connection-oriented (eSCO) logical transport. eSCO provides a point-to-point link between a master transceiver and a specific slave transceiver. It reserves slots on the physical channel and can therefore be considered as a circuit-switched connection between the master and the slave. eSCO links also can offer limited retransmission of packets in the slots that follow the reserved slots. Otherwise these slots may be used for other traffic.